This invention relates to disk play-back machines and more particularly to improvements in tangentially tracking transducer arm assemblies therefor, whose vertical and horizontal pivots are mounted on a carriage for movement along a track and in a plane parallel to the surface of the record disk to be reproduced.
All transducer arm assemblies of the aforementioned type commonly slide along a track whose length is at least as great as the distance, measured along the radius, between the largest modulated groove radius of a long playing record disk and the smallest modulated groove radius of said disk. The largest modulated groove radius and the smallest modulated groove radius of a standard long playing record disk is 5.720" and 2.362" respectively, which results in a track length of 3.358". These tracks are actually longer though, since the tranducer arm support carriage must be allowed to slide into a rest position. Because of these facts, transducer arm assemblies of the aforementioned type are quite long and usually require one entire side of a turntable base for mounting space. At least one after market transducer arm assembly of the aforementioned type overhangs the side walls of some turntables when it has been mounted properly, precluding closure of the dust cover. In addition to these disadvantages, the sliding carriages introduce mechanical noise which is picked up by the transducer in contact with the record disk for subsequent amplification along with the usable signal from the record disk. Additional disadvantages are introduced by the use of geared down D.C. motors to drive the carriages. These motors must constantly rotate, thus introducing additional mechanical and electrical noise into the play-back system.
Transducer arm assemblies of the aforementioned type, which do not use servo systems, and whose transducer arms are rigidly connected to their carriage, rely on ultra low friction track assemblies but suffer from the problem, that the transducer arm stylus, as it is in contact with the groove in the surface of a record disk "sees" the entire mass of the transducer arm in the horizontal plane.